Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$223.54	10.694%	$247.4454	$247.45	$247.45	$247.40
Purchase #2	$155.35	10.126%	$171.0807	$171.08	$171.10	$171.10
Purchase #3	$10.28	12.269%	$11.5413	$11.54	$11.55	$11.50
Purchase #4	$155.50	4.445%	$162.412	$162.41	$162.40	$162.40
Purchase #5	$182.47	7.260%	$195.7173	$195.72	$195.70	$195.70
Purchase #6	$47.40	11.426%	$52.8159	$52.82	$52.80	$52.80
Purchase #7	$209.60	7.754%	$225.8524	$225.85	$225.85	$225.90
7 purchase totals =	$984.14		$1,066.8650	$1,066.87	$1,066.85	$1,066.80